1. Field of the Invention
The present invention relates to a moving picture decoding apparatus and a picture boundary deciding method.
2. Description of the Related Art
A method of coding a moving picture includes MPEG-4 and H. 264/MPEG-4 AVC obtained by developing the MPEG-4 (which will be hereinafter referred to as “H. 264”. “See Draft ITU-T Recommendation and Final Draft International Standard of Joint Video Specification (ITU-T Rec. H. 264|ISO/IEC 14496-10 AVC), “in Joint Video Team of ISO/IEC MPEG and ITU-T VCEG, May 2003). The H. 264 is a moving picture coding method employed for a terrestrial digital broadcast (see “ARIB TR-B14, Terrestrial Digital Television Broadcasting Application Rule Technical Material”, Association of Radio Industries and Businesses, 2004 and “ARIB TR-B13”, Terrestrial Digital Voice Broadcasting Application Rule Technical Material”, Association of Radio Industries and Businesses, 2004), 3GPP, HD-DVD and the like. Referring to a mobile terrestrial digital broadcast, application rules are created based on the ARIB (see “ARIB TR-B14, Terrestrial Digital Television Broadcasting Application Rule Technical Material” Association of Radio Industries and Businesses, 2004) and a service will be started at the end of 2005. Referring to a mobile broadcast which has already been serviced, similarly, a transition from the MPEG-4 to the H. 264 has been investigated as a moving picture coding method.
In the broadcasting application of the H. 264, an H. 264 stream is multiplexed to MPEG-2 systems (see ISO/IEC 13818-1) together with information such as a voice and data broadcast and the like and is transmitted to a receiving terminal. In a radio distribution for a moving picture utilizing an IP network or the like, moreover, the H. 264 stream is multiplexed by RTP (Real-time Transport Protocol). However, since the receiving terminal is moved, the stream cannot be expected to be always received in a stable radio environment. In an environment in which the receiving terminal is hidden by a building or the like, particularly, an error is mixed into the stream very often. Accordingly, an error resistant function is indispensable to a decoder to be used in an error environment. Since an error resistant processing in the H. 264 is nonstandard, however, a behavior thereof is varied depending on a decoder and various proposals have been given (see Y.-K. Wang, M. M. Hannuksela, V. Varsa, A. Hourunranta, and M. Gabbouj, “The error concealment feature in the H.26L test model, “Proc. ICIP, vol. 2, pp. 729 to 732, September 2002., V. Varsa, M. M. Hannuksela, and Y.-K. Wang, “Non-normative error concealment algorithms, “ITU-T VCEG-N62, September 2001. and Hirofumi Mori, Hirokazu Kawakatsu, Masakazu Suzuki, “Investigation related to Reproduced Image in Error Environment in H. 264” Technical Report of IEICE, IE 2004-18, May. 2004).
On the other hand, in the H. 264, a syntax to be used for deciding a slice picture boundary (hereinafter referred to as a “picture boundary” in this specification) is present in all slice pictures. For this reason, there is a problem in that the syntax is damaged by an error. When the error is mixed into the syntax, therefore, the picture boundary is decided erroneously. Consequently, the number of pictures to be decoded is increased or decreased. Thus, there is a problem in that a mismatch of a reference frame, an overflow of a decoder buffer, an increase in a throughput, and the like are caused.